Researchers want to leverage the centuries-old art of cutting paper, kirigami, into designs to develop a sensor sheet that can stretch and breathe with the skin while collecting electrocardiographic data. Scientists in Japan use cuts in a film made of polyethylene terephthalate printed with silver electrodes to fit a sensor on a person’s chest to monitor his or her heart. At the optimal size found, they were able to detect enough signal from the heart to be used in a smartphone app.